What are the possible false positive and false negative findings on radiography for transitional cell carcinomas (TCCs)?

Answer

Calcification is seen in 10% of renal cell carcinomas. Retroperitoneal tumors, infections, or inflammation; pelvic tumors; pelvic lipomatosis; and gynecologic and gastrointestinal pathologies may cause extrinsic ureteric obstruction. Other causes of ureteric obstruction or bladder abnormalities include irradiation, surgery, trauma, or infections such as tuberculosis or schistosomiasis. These conditions may result in telltale signs on plain radiographs.

Other causes of filling defects may mimic a TCC, such as radiolucent or uric acid stones; blood clots; sloughed papilla caused by papillary necrosis; or fungal balls in patients with diabetes. Vessel crossing may cause a linear extrinsic impression; in these cases, oblique or compression images may help in differentiating TCCs from urothelial tumors. Tuberculosis can cause narrowing of the infundibulum and irregular calices. With regard to imaging, tuberculosis is the major disorder in the differential diagnosis.

Other mimics include pyeloureteritis cystica, renal cell carcinoma invading the pelvicaliceal system, or choleastoma. Squamous cell carcinoma (SCC) is radiographically indistinguishable from TCC; however, SCC is less likely to be a polypoid tumor. Although a diagnosis may be made on the basis of urograms or cystograms, a small bladder tumor, especially one of the infiltrative types, may go undetected. Furthermore, a dense concentration of contrast material may obscure the intraluminal part of the urothelial tumor.

Mimics of ureteric TCC include papilloma or polyp, which commonly produces a long, smooth intraluminal filling defect. This defect may prolapse up and down the ureter on serial images, and it may even intussuscept. Avoiding the introduction of air bubbles is important because these could be mistaken for tumors.

A 21-year old man presented with a history of intermittent hematuria of 1-month duration. Three months previously, he had been assaulted and kicked in the right loin. A 30-minute intravenous urogram shows a moderate right hydronephrosis without filling of the renal pelvis, although some contrast material has passed into the upper ureter. Note also a polypoid intraluminal filling defect within the left side of the bladder (arrow).

Left, transverse sonogram of the right kidney in the same patient as in the previous image shows a centrally placed solid mass within the renal pelvis with low-level echoes and with proximal hydronephrosis. Right, transverse sonogram through the bladder shows a polypoid filling defect in the bladder.

Nonenhanced (top) and enhanced (bottom) CT scans through the kidneys show a mass in the right renal pelvis. The histologic diagnosis was a right renal pelvis neurofibroma and a bladder transitional cell carcinoma.

An intravenous urogram in a 36-year old woman who presented with evidence of a urinary tract infection and gross hematuria. A 10-minute intravenous urogram shows a filling defect in the lower pole calyx on the right. A provisional diagnosis of transitional cell carcinoma was made. Subsequent investigations and the course of events proved that the filling defect was caused by a blood clot related to the hematuria secondary to acute pyelonephritis.

Localized views of the right vesicoureteric junction obtained after intravenous urography shows a polypoid filling defect in the lower right ureter due to a transitional cell carcinoma.

A 10-minute intravenous urogram in a 56-year-old man presenting with hematuria. The image shows a mass lesion in the right renal pelvis that bisects the renal sinus and splays the adjacent calyces.

Longitudinal sonogram obtained through the right kidney shows a hypoechoic mass bisecting the renal sinus fat. The mass is a transitional cell carcinoma.

Nonenhanced (top) and enhanced (bottom) CT scans obtained through the kidneys in a 73-year-old woman show a mass in the left renal pelvis is a transitional cell carcinoma.

Left retrograde pyelogram shows marked irregularity of the infundibulum of the upper pole calyx caused by infiltration by transitional cell carcinoma. This information was unavailable on the CT scans.

Top, Longitudinal sonogram obtained thorough the left kidney in a 58-year-old man presenting with hematuria shows a normal left kidney. Bottom, More medial section through the same kidney shows a vague isoechoic mass in the upper of the kidney. Whether this finding represented an artifact or a genuine lesion was unclear. Technetium-99m dimercaptosuccinate (99mTc DMSA) scanning is good modality for differentiating a renal pseudomass from a genuine mass.

Left posterior view of a technetium-99m dimercaptosuccinate (99mTc DMSA) scan shows a photon-deficient mass in the upper pole of the left kidney; this finding indicates a genuine mass in this region. At partial nephrectomy, transitional cell carcinoma was confirmed.

Scout radiograph in a 53-year-old man presenting with hematuria shows a few small vague opacities in the left renal area; these are suggestive of renal calculi.

Longitudinal sonogram through left kidney shows that the filling defects are due to calculi. Ultrasonography is an efficient means for differentiating between radiolucent calculi and uroepithelial tumors.

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